The present invention is directed to a method and apparatus for interior cleaning of pipes, vessels, and other equipments which are contaminated with metallic sodium or other highly reactive chemical constituents. Typically, such contamination includes process related greases, sludges, and other materials. This process features the introduction of a non-reactive carrier solvent which is formulated to contain a small percentage of water. The carrier solvent and water combination (either a solution or emulsion) have solvent properties which will dissolve or disperse salts, oils, greases and other contaminants which might otherwise coat over the reactive metals and prevent access of the wet solvent to the underlying metallic sodium. Metallic sodium is exposed to react with the water in the solvent to generate sodium hydroxide and hydrogen. The heat released by this reaction and the reaction products are removed from the vessel, piping, or equipment being cleaned by the circulating solvent. The process related sludges are stripped and carried away by the solvent.